An organic electroluminescent element (hereinafter, referred to as “organic EL element”) utilizing electroluminescence (hereinafter, referred to as “EL”) of an organic material is a thin-film type completely-solid state element capable of emitting light at a low voltage of approximately several volts to several tens of volts, and has many excellent features such as high luminance, high light emission efficiency, small thickness and light weight. Accordingly, particularly in recent years, OLED having a barrier film of small thickness and light weight on a resin base material has attracted attention, as backlights for various kinds of displays, display boards such as a signboard and an emergency lamp, and surface emitting bodies such as illumination light sources.
With respect to these requirements to the barrier film, a barrier film having a high barrier property and smoothness, which is more suitable for the organic EL element has been proposed (for example, refer to Patent Literature No. 1). According to the method described in Patent Literature No. 1, the barrier film is formed by a vapor deposition system. An accumulated film like the vapor deposition system has a limitation on improvement of smoothness, and further improvement technique of the smoothness.
Furthermore, by introducing a smoothing layer to the surface of a barrier film, a technique that can simultaneously give both high barrier property and smoothness has been proposed (for example, refer to Patent Literature No. 2). However, although a smoothness can be obtained according to Patent Literature No. 2, the barrier property is not enough, and thus the storability of the organic EL element is poor.
Moreover, a technique that simultaneously gives both high barrier property and smoothness has been proposed by subjecting the barrier film of the vapor deposition system to eximer treatment and further forming a polysilazane layer (for example, referring to Patent Literature No. 3). However, according to Patent Literature No. 3, in the production process of an organic EL element, in which an adhesive strength between the vapor deposition film and the polysilazane layer is lowered and the bending characteristics of the organic EL elements is deteriorated.